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ISIN Validator

Check whether a security's ISIN is valid.

Result

Valid
5

How it is calculated

An ISIN has 12 characters: a two-letter country code, a nine-character alphanumeric identifier and a final check digit. The tool first checks this layout (the check digit must be a number). Then each letter is replaced by two digits, A = 10 … Z = 35. The final digit is removed, and the Luhn algorithm is applied to the rest from right to left: double every second digit starting with the rightmost, subtract 9 from any result above 9, and add all digits. The expected check digit is (10 − sum mod 10) mod 10.

Lower-case letters and spaces at the ends are accepted. A "Valid" status means only that the check digit fits, so a typing error is unlikely; it does not prove that the security exists or who issues it.

Worked example

Take US0378331005. Letters become digits: U = 30 and S = 28, so the first eleven characters give 3028037833100. Doubling every second digit from the right and adding gives a sum of 45. The expected check digit is (10 − 5) mod 10 = 5. The last character of the code is 5, so the tool shows the status Valid with check digit 5.

Try this example →

Common mistakes

  • Treating "Valid" as proof that the security exists; only the arithmetic is checked.
  • Typing the letter O instead of the digit 0, or I instead of 1.
  • Adding spaces or hyphens inside the code: only the 12 characters are accepted, and a malformed code gives no result.
  • Confusing ISIN with a ticker symbol or a CUSIP; they have different lengths and are issued separately.

About this calculator

This tool validates a 12-character ISIN (International Securities Identification Number), the global standard (ISO 6166) for uniquely identifying a specific securities issue — stocks, bonds, and other instruments. An ISIN consists of a 2-letter country code, a 9-character alphanumeric national security identifier, and a single check digit computed with a variant of the Luhn algorithm after converting letters to numbers.

Custodians, brokers, exchanges, and back-office settlement systems use ISIN validation to catch typos before trades are booked, since a single wrong character can route an order to the wrong security. Enter an ISIN to check whether its check digit is valid and see the algorithm confirm it matches the expected format.

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